Korean IME: composing character still moves to wrong position on arrow key press (v1.24.11321.0)

[dongy703]

Description

When composing a Korean (Hangul) character and pressing an arrow key before the composition is finalized, the composing character is inserted at the new cursor position instead of staying at the original position.

This was reportedly fixed in #20039 and #20041, but the issue still reproduces on v1.24.11321.0 (stable).

Steps to reproduce

1. Open Windows Terminal (any shell: cmd, PowerShell, or WSL bash)
2. Type Korean text, e.g. 가나 and begin composing the next character (e.g. ㄷ)
3. Before finalizing the composition (without pressing Space/Enter), press an arrow key (← or →)
4. The composing character (ㄷ) moves to the cursor's new position

Expected behavior

The composing character should be finalized at its original position before the cursor moves.

Actual behavior

The composing character follows the cursor and is inserted at the wrong position.

Environment

• Windows Terminal: v1.24.11321.0 (stable)
• Windows: 23H2
• Shells tested: cmd, PowerShell 5.1, WSL2 bash
• Microsoft IME (legacy mode)
• conhost.exe does NOT have this issue — only Windows Terminal

[lhecker]

I may have accidentally broken this behavior when I changed the PR to be more performant. I apologize!
It may take me some time to get around to this, so if anyone has a chance to debug this, it would help me a lot.

[Geol2]

I've confirmed the root cause.

The fix from #20039 (HasActiveComposition() guard in TermControl::_KeyHandler)
was merged into main but has not been cherry-picked into release-1.24.

Checked origin/release-1.24 branch — the guard is absent in TermControl.cpp
around line 1795, which is why v1.24.11321.0 (stable) still reproduces the issue.

Reproduces with: Legacy Microsoft IME enabled, composing Korean character + arrow key press.

A cherry-pick of commit 14f427195 (Fix Korean IME arrow key inserting character at wrong position #20039)
into release-1.24 should resolve this.